In a typical cellular system, also referred to as a wireless communications network, wireless terminals, also known as mobile stations and/or user equipment units communicate via a Radio Access Network (RAN) to one or more core networks. The wireless terminals can be Machine-to-Machine (M2M) devices, Internet-of-Things devices, mobile stations or user equipment units such as mobile telephones also known as “cellular” telephones, and laptops with wireless capability, for example, portable, pocket, hand-held, computer-comprised, or car-mounted mobile devices which communicate voice and/or data with radio access network.
The radio access network covers a geographical area which is divided into cell areas, with each cell area being served by a base station, e.g., a Radio Base Station (RBS), which in some networks is also called “NodeB” or “B node” or “Evolved NodeB” or “eNodeB” or “eNB” and which in this document also is referred to as a base station. A cell is a geographical area where radio coverage is provided by the radio base station equipment at a base station site. Each cell is identified by an identity within the local radio area, which is broadcast in the cell. The base stations communicate over the air interface operating on radio frequencies with the user equipment units within range of the base stations.
In some versions of the radio access network, several base stations are typically connected, e.g., by landlines or microwave, to a Radio Network Controller (RNC). The radio network controller, also sometimes termed a Base Station Controller (BSC), supervises and coordinates various activities of the plural base stations connected thereto. The radio network controllers are typically connected to one or more core networks.
The Universal Mobile Telecommunications System (UMTS) is a third generation mobile communication system, which evolved from the Global System for Mobile Communications (GSM), and is intended to provide improved mobile communication services based on Wideband Code Division Multiple Access (WCDMA) access technology. UMTS Terrestrial Radio Access Network (UTRAN) is essentially a radio access network using wideband code division multiple access for user equipment units (UEs). The Third Generation Partnership Project (3GPP) has undertaken to evolve further the UTRAN and GSM based radio access network technologies. Long Term Evolution (LTE) together with Evolved Packet Core (EPC) is the newest addition to the 3GPP family.
A Public Land Mobile Network (PLMN) is a network established and maintained by an operator. An operator provides mobile services to wireless devices through its PLMN. A PLMN is identified by a Mobile Country Code and a Mobile Network Code. A PLMN which a wireless device is registered to is referred to as a home wireless network. Once a wireless device travels to another PLMN, other than the home wireless network, this is referred to as a roaming state. In a roaming state, a wireless device is served by a visiting PLMN, which is referred to as a visiting wireless network.
In LTE, roaming is done either by local breakout or home routing. In local breakout, the home operator will receive information about the usage from the remote network, by using, for example, 3GPP's Policy and Charging Control Architecture. EPC handles Mobility Management and breakout in core network nodes such as the MME, SGW and/or PGW.
In current deployments, the visited network operator usually own the infrastructure as well as the network services and conforms to a set of 3GPP standards to handle roaming and breakout, either local or home routing. Similar architecture is used both for Voice over LTE and data. Charging and subscriber usage information is exchanged between the visited network and home network via Policy and Charging Rules Function 30 (PCRF) nodes. Such procedures are further described in 3GPP TS.23.203 and GSMA IR.88 LTE Roaming Guidelines, Version 6.0, 31 Aug. 2011.